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The multi-objective optimisation of high-speed rail profile with small radius curve is studied in the paper. A multi-objective mathematical model for rail profile optimisation of high-speed railway is established. The CN60 rail profile is parameterised into a series of generalised functions of design variables. In order to guarantee the smoothness of the rail profile and meet the maximum grinding depth of rail in China, the constraints are employed. The wheel-rail vertical clearance and equivalent conicity of wheelset are taken as objective functions, and a rail wear prediction programme is compiled. Contact line method is employed to complete the detection algorithm of wheel-rail contact points. Finally, NSGA-II Algorithm is adopted to solve the Pareto-optimal front of the optimisation model. A set of solutions are retrieved from the Pareto optimal front solution as the optimised profile. The optimised rail profile and the original rail profile are matched with the LMA wheel profile (a certain worn type of wheel profiles for EMU in China) respectively. It is testified that the rail profile could effectively reduce the rail wear and improve curving performance. The new method proposed in this paper can provide some reference for the optimisation design of high-speed rail profile with small radius curve. [ABSTRACT FROM AUTHOR]

To reduce the complexity of monitoring and management of robots in service, a six-axis robot control system based on digital twin is proposed. Based on 3D printing technology, a six-axis robot is developed. At the same time, the kinematics of the robot is analyzed, and its kinematics model is built using the D-H rule. The forward and reverse kinematics of the robot are solved. Through the two-way data interaction between the model layer and the entity layer, the simulation operation of the robot and the twin synchronous operation of the virtual real robot are realized. Based on the real-time data drive, the key parameters of the robot are monitored, and the health parameter table of the current, voltage, joint vibration, and other parameters of the robot system is established. Based on the idea of comparison of the same kind, the abnormal state detection of the robot is realized through quantitative analysis. Finally, the feasibility of the proposed system is verified by experiments. [ABSTRACT FROM AUTHOR]

The high-frequency excitation generated by the wheel polygon seriously affects the safety of the train. In order to explore the evolution mechanism of wheel polygonisation, a long-term prediction model of wheel circumferential wear on both sides of the wheelset is proposed. Based on a new updating strategy, the model is implemented by combining the coupled vehicle/track dynamic model and the wheel circumferential wear model. The wheel circumferential wear model is implemented by local tangential contact model FaStrip and USFD (a wear model proposed by The University of Sheffield). By analysing the measured data, five wheel circumferential states are summarised, which are employed as wheel non-circular excitations to analyse the evolution of the wheel polygons on both sides of the wheelset. The results show that the same order of the polygonal wheels on both sides of the wheelset is the main reason for the evolution of the order of polygonal wheels in integer multiples. When the circumferences of the wheels on both sides are in an asymmetric state, the wheels on both sides will interact with each other, and the final circumferences of the wheels will gradually evolve into mixed polygonal circumferences related to the initial orders. [ABSTRACT FROM AUTHOR]

This study investigates 1.5 generation Asian immigrant children's (n = 264) early literacy achievement patterns, treating them as a heterogeneous group. Specifically, the within-group variances in reading achievement from kindergarten to third grade are examined, drawing on four waves of data from the ECLS-K class of 1998-1999. Our analysis shows that ethnicity plays a role in shaping the children's initial reading readiness and later growth, but the effects of languages spoken at home are not significant. Our analysis also demonstrates a persistent achievement gap between low-and high-socioeconomic status (SES) Asian groups. However, gender difference in terms of children's reading development is not found to be significant. There is also no interaction between SES and the other factors such as gender, ethnicity and language backgrounds.

Drawing on research about East Asian (mainly Chinese, Korean, and Japanese) heritage language (HL) teaching and learning in three contexts--the home, community heritage language schools, and programs in U.S. K-12 schools--this article discusses the challenges that East Asian subethnic groups face in improving HL education in each context. Specifically, the review finds that in the home context, parents' practices in HL maintenance are complicated by factors such as parents' attitudes and beliefs about language maintenance and literacy resources. While community language schools have been recognized as the strongest efforts for teaching HLs, these schools often face various challenges in getting the human and physical resources they need. Finally, the review reveals the lack of a supportive environment for HL maintenance in K-12 schools. The findings suggest an urgent need for realignment among federal policies, mainstream school curricular, and community practices in order to maximize the full potential of the United States becoming multilingual in a globalized society.

The precision instruments and equipment are often utilized in low-frequency and micro-amplitude vibration systems, in which many vibration isolators of rubber materials are widely used. Ignoring the low-frequency amplitude will result in errors in the fatigue life design of the vibration isolators and predicting the dynamic response of each frequency band accurately becomes necessary. However, integer-order models cannot describe the frequency dependence of rubber materials, while the fractional-order models can describe it instead. On the other hand, the elastic restoring force is strongly nonlinear under large deformation, and the vibration of the nonlinear system contains multiple harmonic components. In order to solve those issues, the fractional nonlinear Nishimura model is used to characterize the constitutive relation of vibration isolators such as air springs, which are made of carbon black filled natural rubber. The high-order harmonic balance method is used to obtain the steady-state response of the vibration system, while the fourth-order Runge–Kutta method is applied to simulate the dynamic response of the system in the low-frequency region, and the Lyapunov exponent is used to determine the stability of the system. Furthermore, the influence of parameters on the amplitude–frequency characteristics of different frequency bands is also studied, and a method to solve the optimal damping coefficient is proposed based on the primary resonance amplitude–frequency curves. The results show that there is a diversity of periodic motions in the process of adjacent super-harmonic resonance transition. Numerical simulations also demonstrate that multi-periodic motions coexist in the system. The motion transition law between the polymorphic coexistence region and its adjacent regions is summarized. [ABSTRACT FROM AUTHOR]

How do second-language learners become successful readers and writers? This article examines the importance of social networks to English language learners' reading and writing development. It describes different family, peer, and virtual social networks that ELLs can utilize to engage in online and offline reading and writing (especially related to youth popular culture, such as fan fiction) outside school. The article highlights the importance of fostering a participatory culture in classrooms and schools to help ELLs form communities of learners and supporters and facilitate their second-language literacy development. (Contains 2 notes.)

Drawing on survey data, this paper examines the patterns and perceptions of technology use by primary EFL teachers in China. Findings suggest that although Chinese EFL teachers hold positive attitudes toward the value of technology for teaching and learning, they use technology mainly for teacher-centered purposes, such as teaching preparation and instructional delivery, and seldom utilize technology for student-centered activities. Factors constraining student-oriented technological use in early EFL instruction include teacher-center pedagogical practices and lack of effective professional development that focuses on instructional design and technology integration. These findings suggest that China must redirect its effort to promote teacher conceptual and pedagogical change in integrating technology in early EFL instruction and emphasize alignment among technology, curriculum, and pedagogy in EFL teaching. (Contains 8 tables.)

Task-based language teaching (TBLT) has been drawing researchers' and practitioners' attention since its onset in the 1980s. The rich and still expanding literature on TBLT is helping to mature both its theoretical conceptualization and practical implementation in foreign and second language education. Technology has played and will continue to play an important role in this maturation process. This review focuses on the intersection of technology and TBLT, examines the mutual contributions of technology and TBLT to each other, and discusses the challenges in implementing and researching TBLT in technology-mediated environments. In addition, this review outlines a set of crucial issues to which attention must be paid to further develop technology-enhanced TBLT.